This invention encompasses solid detergent compositions comprising a surface-active agent selected from the group consisting of anionic, nonionic, zwitterionic, and ampholytic surfactants, and mixtures thereof, and a paticular type of soil release polymer comprising ethylene terephthalate and polyethylene oxide terephthalate in particular ratios and proportions. The detergent compositions herein clean and provide improved soil release benefits to synthetic fabrics, particularly polyester fabrics, as compared with known soil release agents employed in detergent compositions.
Much effort has been expended in designing various compounds capable of conferring soil release properties to fabrics woven from polyester fibers. These fabrics are mostly co-polymers of ethylene glycol and terephthalic acid, and are sold under a number of tradenames, e.g., Dacron, Fortrel, Kodel and Blue C Polyester. The hydrophobic character of polyester fabrics makes their laundering (particularly as regards oily soil and oil stains) difficult, principally due to the inherently low wettability of the polyester fibers. Since the character of the fiber itself is hydrophobic, or oleophilic, once an oily soil or oily stain is deposited on the fabric it tends to be "attached" to the surface of the fiber. As a result, the oily soil or stain is difficult to remove in an aqueous laundering process.
When hydrophilic fabrics such as cotton are soiled by oily stains or oily soil, it is well-recognized that the oil is much more easily removed than in the case of hydrophobic polyester fabrics. This difference in oil removal characteristics is apparently caused by a greater affinity of cotton fabrics for water. The differing hydrophilic/hydrophobic characteristics of cotton and polyester are due in part to the basic building blocks of the fibers themselves. That is, since polyester fibers are copolymers of terephthalic acid and ethylene glycol, they have less affinity for water because there are fewer free hydrophilic groups, e.g., hydroxyl or carboxyl groups, where hydrogen bonding can occur. With cotton, which is a cellulose material, the large number of hydrophilic groups provides compatibility with, and affinity for, water.
From a detergency standpoint, the most important difference between hydrophobic fabrics and hydrophilic fabrics is the tendency for oily soil to form easily removable droplets when present on a hydrophilic fabric and in contact with water. The mechanical action of washing and the action of synthetic detergents and builders normally used in the washing step of the laundering process removes such oil droplets from the fabric. This droplet formation is in contrast to the situation which exists with a polyester (hydrophobic) fiber. Water does not "wick" well through hydrophobic fabrics and the oily soil or stain tends to be retained throughout the fabric, both because of the inherent hydrophobic character of the fabric and the lack of affinity of oily soils for water.
Since polyester and polyester-blend fabrics (e.g., polyester-cotton blends) are susceptible to oily staining, and, once stained, are difficult to clean in an aqueous laundry bath, manufacturers of polyester fibers and fabrics have sought to increase the hydrophilic character of the polyester to provide ease of laundering.
A number of approaches to the problem of increasing the hydrophilic character of polyester fabrics and fabric blends have been taken. Many of these approaches involve a process employed by the textile/fiber manufacturer or the textile manufacturer. Netherlands Application 65/09456 [see also D. A. Garrett and P. N. Hartley, J. Soc. Dyers and Colourists, 82, 7, 252-7 (1967) and Chem. Eng. News, 44, 42-43 (Oct. 17, 1966)] describes the treatment of polyester fabrics in which a copolymer of terephthalic acid with a polyethylene glycol is padded onto the polyester fiber using an emulsion containing a 20% concentration of the padding agent, a polyester swelling agent such a benzyl alcohol, and heat. The object of this treatment is to give the basic polyester fiber more hydrophilic character, thereby reducing the tendency of the polyester fiber to retain oily stains.
Different polyester fabric finishing techniques are, for example, described in: German Pat. No. 1,194,363; Netherlands Application 65/02428; Belgium Pat. No. 641,882; and French Pat. No. 1,394,401.
British Pat. No. 1,088,984 relates to a modifying treatment for polyester fibers whereby a polyethylene terephthalate polymer is applied to the surface of said fibers. The polymers employed contain ethylene terephthalate and polyethylene oxide terephthalate units at a molar ratio from 1:1 to 8:1. The polyethylene oxide used for preparing these polymers has a molecular weight in the range of 300 to 6,000, preferably from 1,000 to 4,000.
British Pat. No. 1,175,207 discloses a process for treating filaments and fibers by contacting same with polyesters containing from about 10 to about 50% by weight of crystalline polyester segments which are identical with the repeat units forming the crystalline segment of the polyester fiber, and from about 50 to about 90% by weight of water solvatable polyoxyalkylene ester segments. The polymers employed appear to be identical to those disclosed in British Pat. No. 1,088,984.
British Pat. No. 1,092,435 deals with a stable dispersion of water-insoluble graft polymers containing polyoxyethylene glycol and polyethylene terephthalate. These polymers have a ratio of ethylene terephthalate to polyoxyethylene terephthalate from about 2:1 to about 6:1. Also, the teachings of British Pat. No. 1,119,367, and Dutch Pat. No. Application 66/14134, relate to the application to fibers of surface modifying agents as described in the patents referred to hereinabove.
U.S. Pat. No. 3,712,873, Zenk, discloses the use of polyester polymers in combination with quaternary ammonium salts as fabric treatment compositions. Terpolymers having a molecular weight in the range from 1,000 to 100,000, and a molar ratio of terephthalic acid:polyglycol:glycol from 4.5:3.5:1 are disclosed. Co-pending application U.S. Ser. Number 328,824, filed Feb. 1, 1973, Bassadur, now U.S. Pat. No. 3,893,929, relates to compositions and processes for imparting renewable soil release finish to polyester-containing fabrics. Polyesters based on terephthalic acid, ethylene glycol and polyethylene oxide, and their use in acidic fabric rinses, are disclosed. The polymers have a molecular weight in the range from 1,000 to 100,000, and the polyethylene oxide link has a molecular weight of 1300 to 1800.
The concurrently filed U.S. patent application Serial Number 482,948, inventor, Charles H. Nicol, entitled LIQUID DETERGENT COMPOSITIONS HAVING SOIL RELEASE PROPERTIES, discloses compositions comprising nonionic surfactants, ethanolamine-neutralized anionic surfactants, free ethanolamine and a soil-release polymer which can be identical to the novel polymers employed herein.
The prior art polymers do not provide an optimum solution to the soil release problem inherent with any hydrophobic fiber mainly because of lack of durability and marginal-to-unsatisfactory soil release performance. Moreover, many of the prior art soil release polymers lack the necessary substantivity to fibers under conditions of neutral-to-alkaline pH, i.e., under common laundering conditions. In addition, some of the known polymers seem to require calcium ions for fiber substantivity. Of course, the presence of free calcium or other water hardness cations is preferably avoided in a laundering operation.
It has now been found that certain hydrophilic terephthalate-based polymers having critical ratios of monomer units as well as critical limitations on the molecular weight of the hydrophilic moieties in the polymers are particularly useful as soil release agents. The in-use superiority of the polymers herein over those of the prior art is surprising in that nothing in the vast literature in this area suggests that the critical polymer design now provided would have any substantial effect on soil release properties. Moreover, the present compositions are provided in solid granular or powder form and are not limited to the liquid compositions of Nicol, above. This desirable result is made possible by using the polymers disclosed by Hays, below.
The concurrently filed U.S. patent application Ser. No. 482,949, inventor Hugh R. Hays, entitled POLYETHYLENE OXIDE TEREPHTHALATE POLYMERS, the disclosures of which are incorporated herein by reference, describes novel terephthalate polymers composed of ethylene terephthalate and polyethylene oxide terephthalate. Such polymers are capable of imparting soil release properties to synthetic fibers in a dilute aqueous solution. These novel polymers are identical to those now found to be useful in dry granular or powdered detergent compositions.
It is an object of this invention to provide solid detergent compositions capable of simultaneously cleaning and imparting soil release properties to synthetic fibers laundered therewith.
It is an additional object of this invention to provide detergent compositions in solid form capable of conferring effective soil release properties to fabrics, said compositions comprising an organic surface-active agent and a polymer composed of ethylene terephthalate and polyethylene oxide terephthalate, as disclosed hereinafter. The chief advantage of solid detergents over the liquid form is that substantial proportions of detergency builders can be conveniently used in solid compositions of the type disclosed herein.
These and other objects are obtained herein as will be seen from the following disclosures.